On-line mounting, mechanical flow switch, for liquid or gaseous media. Sturdy plastic, aluminum or stainless steel case is optional. Minimal pressure loss, good repeatability, pollution resistance, complete isolation of mechanical and electronic parts, suitable for small flow economy. With switch setting scale, users do not need to set on site. LED display switch status, double switch output is available. Gas liquid dual, industrial automation/mechanical equipment/air compression industry/refrigeration and air conditioning.